benjamin



(No Model.) 3 Sheets-Sheet 1. G. H. BENJAMIN.

UNDERGROUND OONDUIT FOR ELECTRICAL CONDUGTORS. No. 315,225.

Patented Apr. 7, 1885.

WITNESSES SAW (N0 ModeL) 3 Sheets-Sheet 2. G. H. BENJAMIN.

UNDERGROUND GONDUIT FOR ELECTRICAL OONDUQTORS. No. 315,225. PatentedApr. 7, 1885.

izoiV/Z L m m Ks! v Y/ \J 7 WITNESSES INVENTOR (No Model, 3 Sheets-Sheet3. G. H. BENJAMIN.

UNDERGROUND OONDUIT FOR ELECTRICAL OONDUGTORS. No. 315,225. Patented Apr.'7, 1885.

INVENTOR w FAQ-FRAN- WITNESSES M 0mm} NS MN UNITED STATES PATENT OFFICE.

GEORGE H. BENJAMIN, OF SHORT HILLS, NEIV JERSEY.

UNDERGROUND CONDUIT FOR ELECTRICAL CONDUCTORS.

SPECIFICATION iormizzv part of Letters Patent No. 315,225, dated April7, 1885.

Application filed July ll 1884. (No model.)

To all whom it may concern:

Be it known that I, GEORGE H. BENJAMIN, of Short Hills, Essex county,State of New Jersey, have invented certain new and useful Improvementsin Underground Pipes or Oonduits for Gonveying Electrical Conductors, ofwhich the following is a specification.

My invention relates to the means and apparatus employed for conveyingelectrical con ductors under ground, and in such a manner that theseparate wires or conductors through which the electric currents aretransmitted shall be properly insulated from each other, the metallictubes, conduit, and the earth, and at the same time, by reason of theparticular arrangement and material of the different parts, theinductive effects of the electric currents transmitted by such electricconductors each upon the other shall, in a measure, be avoided.

My invention consists of inclosing within an outer pipe or conduit anumber of smaller tubes, each arranged to contain a single wire orconductor. The outer pipe or conduit can be of sheet-iron rolled inliquid asphalt, or of any material such as can be used for the purpose.The inner inclosing-tubes, which in their material and method ofconstruction constitute one essential feature of my device, I make ofpaper or cloththat has been treated with any resinous compound and whichis a non -conductor of electricity. These tubes are enveloped in anenvelope or covering of tin-foil and sheet-lead, or sheet-lead alone, or

an alloy of lead and tin. Ihave found, however, by experience, that thegreater proportion of lead in the covering the more useful it becomes inpreventing, absorbing, or cutting off induced currents transmittedbetween currents conveyed by separate conductors in separate tubes.

In order to sustain the small tubes, made as described, within theinclosing pipe or conduit and to connect their resinous or metallicsurfaces together, I provide a number of disks, made of metal ormetallic netting, through which holes are perforated of a sizesufficient to receive the small tubes. These disks, which are arrangedequally distant from each other in the inclosing-conduit, I connecttogether by means of copper wires attached to their circumference.

The method of attaching the copper wires is such that alternate disksare connected electrically with the same longitudinal wire, the objectof which construction will hereinafter be more fully described. Thespaces surrounding the separate small tubes I pack with a fine qualityof mineral wool, which I find to be an excellent non-conductingmaterial, owing to the amount of dry air contained in the interstices ofthe fibrous mass. Around the whole, before insertion in the conduit orinclosing-pipe, I wind a layer of .ordinary tarred building-paper. Theconduit as thus formed has attached to its ends coupling boxes similarto those described in United States Letters Patent No. 302,883, grantedto me August 5, 1884.

By the construction as above described I form, so to speak, a largecondenser, wherein the conducting-wire forms one armature and the leadinclosing-tube the second armature, and the resin-treated tube thenon-conducting body interposed between the armatures. To discharge thecharges of electricity which have been induced in the resinous tube andthe me tallic envelope, I provide two wires, one of which is connectedto the resinous or nonconducting tube and the other to the metallicenvelope or external armature of the condenser, each being connected toearth. The effect of this arrangement is in a great measure to cut offthe induced currents. I have found that the lead covering absorbs suchcurrents, thereby becoming charged, or having induced therein currentswhich flow in a direction oppositeto that of the inducing-cur rent. Ihave also found that such currents induce static charges of negativeelectricity in the resin-treated tube. Both the lead tube and theresinous tube being in metallic contact with the earth, the staticcharges or currents induced therein are readily discharged. As aconsequence, the currents transmitted through the separate conductorsare not at all, or but little, influenced by their proximity to eachother.

In the accompanying drawings, which illustrate my invention, similarletters of reference indicate like parts, in which-- Figure I is aview,partially in section, illustrating one form of the wire or conductorinclosing tube, showing the inner resin-treated tube, tin-foil envelope,and lead covering. tached thereto by means of a resinous varnish.

Fig. II is a similar view showing the tube with the lead covering alone.Fig. III is a transverse section of the conduit and innerinclosing-tubes, and showing the metallic disk in elevation, and thewire-inclesing tubes in their position in the conduit. Fig. IV is atransverse section of Fig. II. Fig. V is a transverse section of Fig. I.Fig.VI is a view in outline showing the position of the metallic disksrelatively to each other and the method of making the connections withthe longitudinal wires which support the disks and convey the currentstherefrom. Fig. VII is a view showing the position of the wire disk inthe conduit. Fig. VIII is a view of my conduit as a whole, shownpartially in section and partially in elevation, and showing therelative position of the parts to each other in the conduit withattachment to the coupling-boxes, ground-connections, &c.

In the drawings, A represents the inclosing pipe or conduit, formed,preferably, of sheetiron rolled once or twice upon itself and cov.- eredboth on the outside and inside, as well as between the eonvolutions ofthe sheet-iron, with asphaltum. A pipe formed in this man- I ner I findto be a non-conductor of electricity,

light, strong, and well adapted to stand the moisture of the earth.

I do not limit myself to any particular form, design, or material ofinclosing-pipe or 0011- duit, as it will be understood that the device,as hereinafter described, can be inserted into any pipe, conduit, orsubway made of any material.

B represents a coupling-box attached to the end of the inclosing-pipe.That shown in the drawings, Fig. VIII, represents such a one as I preferto use, and which is described in United States Letters Patent No.302,883, granted to me August 5, 1884.

0 represents such a tube as I use for inclosing the current-conductingwire or conductor, and consists, primarily, ofa tube formed of pa per,cloth, or paper-pulp, thus including wood pulp,which has been treated atany stage of its manufaeture-thatis, during the manufacture of the pulp,cloth, paper, or of the tube itselfwith any resinous substance ormaterial, such, for instance, as ordinary varnish, or a composition, asof beeswax and resin, or of resin in any menstrum which will dissolveit, or a mixture or compound composed of resin, a dissolving medium, andtungs ate of sodium. By resinous material I include gutta-percha, whichcan also be combined with the tun gstate of sodium.

I do not wish to limit myself to any specific compound or treatment ofthe tube, as I claim the use of any material in combination with theother parts, as hereinafter described,which will act in conjunction withthem and at the same time be negatively electrified by induction.

0 represents a thin layer of tin-foil wound around the inclosing-tube,and preferably at D represents the lead envelope inclosing the whole. InFig. II the envelope D, of lead, is shown covering the paper, thetinfoil being dispensed with. I11 this case the lead is fastened to thepaper by means of the varnish, as described.

Instead of using pure lead for the envelope I may make it of any metalcovered with a lead outer surface, or I may use an alloy of lead and anyother metal, or I may use atube of vucanized fiber with a lead-coatingas the enveloping tube.

I may use any substance for an envelope, provided that the outer surfaceof the tube shall be of lead. I have found, however, by experience, thata tube constructed with tinfoil and lead, or lead alone, as coverings,is the most efficacious in absorbing or intercepting the inducedcurrents.

Surrounding the separate tubes and filling the spaces between them Iplace the mineral wool E, which acts as a non-conductor of electricity,and also is a poor conductor of heat, and thus prevents the tubes in theinterior of the conduit from being affected by changes in thetemperature on the outside of the conduit. Mineral wool can beconveniently placed in position by means of the hand. It should bepacked firmly but not compactly. It should be sufficiently firm toretain its position and not settle away from the tubes in the ordinaryhandling to which they are subjected.

G represents a metallic disk such as I use for supporting thewire-conveying tubes. It can be formed in any shapeto fit theouterinclosing conduit, and it can be made of metal, such as iron, tin,or copper, or, preferably, of wire cloth or netting, as shown in thedrawings.

In order to preserve the form of and to keep the disk straight, I fastena wire,F,around the circumference by soldering or other means. Thedisks, as described, are located equally distant from each other in theinclosing-eolr duit, and vary in number depending upon the size andnumber of the wire-convcying tubes which they are to support. In anordinary conduit, say of from six to twelveinchcs in circumference, thedisks or supportingpieces would be'from two and one-half to three feetapart. Attached to the cireum ference of the disks are a number ofcopper wires,II H, of the same length as the inclosing-conduit.

Referring to Figs. VI and VII, details are shown of the method ofattaching the wire I]: II. In Fig. VI the wires H are shown attached bysoldering or other means to the disk G. The wires II are shown attachedto the disk G by means of non-conducting conneetions,as at Theseconnections may be of any form that will answer the purpose.

It will be observed that the disk 6? is elec trically attached to thewires II and insulated from the wires H. Fig. V II shows the method. ofconnecting all the disks in the conduit.

I do not limit myself to any particular ar- IIO rangement for connectingthe disks together, as they may be connected by pairs or in any otherway that may be found desirable. The metallic disks G, by contact withthe metallic envelopes D of tubes 0, connect them all together, thusforming what is equivalent to a single lead plate and one of thearmatures. The disk G is shown connected with the out side surface ofthe resinous inclosing-tubes O, and insulated from the metallicsurfaces, and, as in the case of the metal coverings, connecting all ofsaid resinous tubes together. By this arrangement, as described, I formwhat may be considered a condenser in which all the current-conductingwires form one armature, all the metallic surfaces of the wire-conveying tubes connected together by the metallic disks in contact therewiththe second armature,and all the resin-treated tubes connected togetherthrough the metallic disks the interposed dielectric or non-conductingbody.

In order to discharge the induced charges of electricity, I provide thewires J and J, one of which is connected to the disks G, and the otherto the disks G, and both to the earth.

In order to retain the mineral wool in its place, surrounding thewire-conveying tubes, I cover the entire cylinder with ordinary tarredbuilding-paper, as shown at I. The cylinder as completed is theninserted into the pipe or conduit forming the outercontaining-body,andthecoupling-pieces,of whatever form, are suitablyattached thereto.

lVhere the sheet-iron conduit is used, as described, it is preferable toground the metallic portions, and this maybe done by connecting thesheet-iron to the wire J and the outside directly to the earth.

R represents a wire or electric conductor in its inclosing-tube.

I have stated that I could use tungstate of sodium incorporated with anyresinous compound with which the wire or conductor inclosing tubes aretreated. The object of using this material is to render the said tubesnon-inflammable, so that, should the wire or conductor contained thereinbecome very hot by means of a short circuit or other cause, thedestruction of the inclosing-tube will not affect any other tube nearby,or within the same conduit. The tungstate of sodium, as alsovariousother chemical substances-such as the oXide of aluminium, sulphate andsilicate of sodium,or the sulphate of potassium, or almost any of whatmay be callec neutral salts, and also various heavy earths andminerals-such as talc, gypsum, serpentine, mica, and asbestus can bemixed with a paper or wood pulp during the'process of manufacture, andby their presence tend to prevent combustion. Tungstate of sodium.however, by being freely soluble in water, seems best adapted for use,as it is a poor conductor of elecricity, does not deliquesceand absorbmoisture, even when located under ground, and, further, adds very littleincreased weight to the tubes themselves.

I claim as my invention 1. In a pipe or conduit for conveying electricalconductors under ground, separate wire or conductor conveying tubesconsisting of an inner tube formed from fibrous material treated with aresinous material, and provided with an envelope formed from layers oftinfoil and lead.

2. In a pipe or conduit for conveying ele ctrical conductors underground, a separate wire or conductor conveying tube consisting of aninner tube treated with a non-inflammable material and a resinousmaterial, and an outer envelope formed from layers of tinfoil and lead.

3. In a pipe or conduit for conveying electrical conductors underground, separate wire or conductor conveying tubes made from any fibrousmaterial treated with any non inflammable substance and resinoussubstance, and provided with an envelope composed of lead or an alloy oflead, substantially as de' scribed.

4. In a pipe or conduit for conveying electrical conductors underground,a separate wire or conductor conveying tube made of any fibrous materialtreated with a resinous ma terial, and provided with an envelopecomposed of lead or analloy of lead.

5. In a pipe or conduit for conveying electrical conductors underground, separate wire or conductor conveying tubes made from an innerresin-treated tube provided with a metallic envelope, in combinationwith plates or disks of metal or wire-cloth, supporting and inelectrical contact with the resinous or the metallic portion of saidtubes, substantially as described.

6. In an underground conduit, the combination, substantially as setforth, of the separate conductor-conveying tubes, the metallicsupporting plates or disks, and the means for connecting them together.consisting of the connecting-wires, all the disks in contact with themetallic envelope, and all the disks in contact with the resinousenvelope, the arrangement being such that the wires which connect oneset of disks are insulated from the opposite set of disks, and the meansfor connecting said tubes and disks to earth.

7. In a pipe or conduit for conveying electrical conductors underground, a plate or disk of wire-cloth for supporting and connecting thewire-conveying tubes together, and provided with openings through whichthe said tubes are inserted, substantially as de described.

8. In a pipe or conduit for conveying electrical conductors underground, a plate or disk of wire-cloth for supporting and connecting theinner or outer envelope of said tubes together, in combination with themeans for connecting said plates or disks together, consisting of wiresattached to their outer edge or circumference, and electricallyconnected thereto or insulated therefrom, substantially as described.

9. In a pipe or conduit for conveying electrical conductors underground, the combinamaterial of mineral Wool around and between 20 tion,with an outer inclosing-pipe, of two or more tubes contained therein,made of an inner tube treated with a resinous material and anon-inflammable substance, and provided with a metallic envelope, platesor disks of metal or Wire-cloth for connecting and supporting saidtubes,the non-inflammable fibrous insulating material, thebuilding-paper envelope, and the electrical conductors for connect ingthe tubes and conduit to earth, substanstantially as described.

10. In apipeor conduitfor conveying electrical conductors underground,the combination of an inclosing-pipe made of rolled sheet-iron inasphalt, with two or more tubes contained therein, made of the materialsand treated as described, plates or disks of metal or wire cloth, anon-inflammable fibrous insulating said tubes, an envelope ofbuilding-paper. and electrical conductors for connecting tubes andconduit to earth, substantially as described.

11. In a pipe or conduit for conveying electrical conductors underground, the combination, substantially as set forth, of theconducting-wires within said conduit, and the means whereby the inducedcurrents induced by the currents conveyed on said co11ducting-wires canbe absorbed and carried out of theinclosing' pipe or conduit, consistingof the resinous tube, its metallic envelope, the metal or wireclothsupporting plates or disks, and the ground-connecting Wires.

GEORGE H. BENJAMIN. W'itnesses:

A. E. SEXTON, C. W. BENJAMIN.

